nitary series spark gap with aligned apertures

ABSTRACT

A spark-gap device includes first and second pairs of conductive electrodes supported within first and second insulating spacer means to provide first and second gaps. The gaps are connected in series by joining the rearward portion of one electrode of the first pair to the rearward portion of one electrode of the second pair. The joined electrodes are hollow to provide a chamber therebetween, and are apertured so that an arc discharge at one gap provides illumination of the second gap. As a result of illumination of one gap by a discharge at the other, the gaps break down at substantially the same time. Furthermore, the chamber between the gaps aids in rapidly extinguishing an arc at the first current zero after an over-voltage condition subsides.

I United States Patent [191 E 28,619

Kawiecki Reissued Nov. 18, 1975 [5 1 UNITARY SERIES SPARK GAP WITH2,365,595 1/1939 Roman 313/268 ALIGNED APERTURES 3,303,381 2/1967Yarmovsky 315/36 3.382.402 5/1968 Lafferty 315/36 [75] Inventor: ChesterJ. Kawiecki, Santa Barbara,

Calif- Prinmry E \'aminerNathan Kaufman 73 A I Mf d l I, Attorney,Agent, or FirmKlarquist, Sparkman. Sslgnee gggg Supp Campbell, Leigh,Hall & Whin'ston [22] Filed: Nov. 12, 1973 211 App]. No.: 414,858 57ABSTRACT RltdU.S.Pt tDoc t Rei e a e a en s A spark-gap device includesfirst and second pairs of ssue 0 conductive electrodes supported withinfirst and sec- [64] Patent N05 3,535,825 ond insulating spacer means toprovide first and sec- ISSue-d: 1:970 ond gaps. The gaps are connectedin series by joining PP Noi 713,919 the rearward portion of oneelectrode of the first pair Flled: 18,1968 to the rearward portion ofone electrode of the second U.S. Applications:

Continuation of Ser. No. 298,014, Oct. 16, 1972.

US. Cl. 315/203; 313/325; 317/69 Int. Cl H05g 41/14 Field of Search315/36, 189; 313/196, 217,

References Cited UNITED STATES PATENTS 4/1930 Goodwin ..3l5/36 Berkey etal 313/203 pair. The joined electrodes are hollow to provide a chambertherebetween, and areapertured so that an arc discharge at one gapprovides illumination of the second gap. As a result of illumination ofone gap by a discharge at the other. the gaps break down atsubstantially the same time. Furthermore, the chamber between the gapsaids in rapidly extinguishing an are at the first current zero after anover-voltage condition subsides.

15 Claims, 5 Drawing Figures Reissued Nov. 18, 1975 FIG. 2

LOAD

SPARK GAP 6O CYCLE I20 V. PMS

CHEST ER J. KAWIECKI IN VEN TOR BUCKHORN, BLORE, KLARQUIST & SPARKMANATTORNEYS UNITARY SERIES SPARK GAP WITH ALIGNED APERTURES Thisapplication is a continuation of Ser. No. 298,014, filed Oct. 16, 1972,which is a reissueof US. Pat. No. 3,535 .582.

BACKGROUND OF THE INVENTION Spark-gap devices are frequently employed astransient protectors across voltage supply lines for protectingelectrical equipment from transient surges. For example, such aspark-gap device may be employed as a lightning arrestor providing abreakdown path from line to line, or line to ground, when a lightningsurge occurs. Therefore the surge does not reach [the and destroyelectricalequipment also connected to the line.

It would be desirable to provide protection at a voltage not much higherthan rated line voltage, with discontinuance of the short circuitsubstantially immediately after the overvoltage condition subsides. Thatis, a spark-gap device on an alternating current system shouldextinguish the are by the time of the first current zero after a linesurge disappears. By way of example, a spark-gap deviceset to provide adischarge when the line voltage reaches 350 volts peak should extinguishwhen the line voltage returns to a 170 volt peak, or l20 volt R.M.S.',line voltage. Unfortunately, the ordinary gap set for such a lowbreakdown voltage would restrike in response to the normally impressedoperating voltage resulting in failure of v the spark-gap device.Consequently, a spark-gap device must ordinarily be set for quite a-highbreakdown voltage if it is to extinguish at normal operating voltages.

" SUMMARY OF THE INVENTION Briefly, in accordance with the presentinvention a spark-gap device includes" first and second pairs ofspark-gap electrodes connected in se'ries. The device is constructedsuch that an arc discharge across one gap causes illumination of theother gap whereby the two gaps break down substantially simultaneouslyupon the occurrence of an overvoltage condition thereacross.Furthermore, an enclosed chamber communicates with the gaps to promoteextinguishing of the arc discharge after the cessation of theovervoltage condition. In accordance with apreferred embodiment, oneelectrode of each pair isapertured', and the apertured electrodes arejoined for providing a passage therethrough acting not only to establishillumination of one gap by the other, but also providing an enclosedchamber which promotes extinguishing of an arc discharge after theovervoltage condition is removed.

7 It is accordingly anobject of the present'invention to provide animproved spark-gap device for furnishing enhanced overvoltageprotection.

It is another object of the present invention to provide an improvedspark-gap device which will break down and protect a voltage supply lineat a comparatively low overvoltage value, and which will extinguish thearc at the cessation of such overvoltage condition.

The present invention, both as to organization and method of operation,together with further advantages and objects thereof may best be,understood by reference to the following description taken in connectionwith the accompanying drawings wherein like reference characters referto like elements.

DRAWINGS FIG. 1 is a side view of a spark-gap device according to thepresent invention as supported in a holder;

FIG. 2 is a circuit diagram illustrating application'of a spark-gapdevice according to the present invention;

FIG. 3 is an enlarged longitudinal cross section of a spark-gap deviceaccording to the present invention;

FIG. 4 is an enlarged longitudinal cross section of an extendedspark-gap device according to the present invention', and

FIGS is a transverse cross sectional view of the FIG. 1 spark-gap devicetaken at 55 in FIG. 4.

DETAILED DESCRIPTION Referring to the drawings, and particularly toFIGS. 1 and 3, a spark-gap according to the present invention includescylindrical spacer tubes and 12 preferably taking the form of ceramictubes. The device is quite small, and each of the cylindrical spacertubes may be approximately fivesixteenths inch in diameter andapproximately five-sixteenths inch in length. The spacer tubes are mostclearly shown in FIG. 3 wherein the spark-gap device according to thepresent invention is illustrated in greatly enlarged cross section. Inassembling the spark-gap device according to the present invention, theends of a ceramic spacer tube, for example tube 10, are suitablymetalized as indicated at 14 and 16 with a high temperature metal oralloy, i.e. molybdenum plus manganese. Brazing washers l8 and 20, whichmay be formed of an alloy of silver and copper,

, are suitably positioned upon the metalized ends. Then,

thin-walled hollow electrodes 22 and 24 are inserted I into either endof ceramic tube 10, each of these electrodes being substantiallycylindrical in shape. For example, electrode 22 has a first inner length26 having a first diameter, and a second or outer length 28 of a largerdiameter which approaches the inside diameter of ceramic tube 10. Theelectrode is also provided with an annular flange 30 at its outer endfor making contact with brazing washer 18. Between length 26 and length28 of the electrode, the diameter thereof changes gradually to provide aflared configuration, or a configurationadapted to provide a bellowsaction between the electrode and the ceramic spacer tube as when thermalexpansion and contraction of the members take place. Thethin-walledhollow electrodes 22 and 24 are preferably formed of Kovar,and the ceramic spacer tubes are preferably alumina. A chamber 32 isprovided by the above construction between tube 10 and electrodes 22 and24.

The spark-gap device also includes hollow electrodes 34 and 36,substantially identical to electrodes 22 and 24, respectively, which areinserted within spacer tube 12. As in the case of joining electrodes 22and 24 to spacer tube 10 to provide chamber 32, joinder of electrodes 34and 36 to tube 12 provides interior chamber 42. Ceramic tube 12 ismetalized as indicated at 58 and 60, while brazing washers 62 and 64 arelocated between the spacer tube and the respective electrodes. Thematerials employed for electrodes and for brazing elements are suitablythe same as hereinbefore described in connection with electrodes 22 and24, and tube l0.

Hollow electrodes 24 and 36 are juxtaposed, and a further "brazingwasher 38 is included in the assembly between-the flanges of electrodes24 and 36 whereby these electrodes are joined together in a seriescircuit.

There is thereby also formed a chamber 40 substantially separate fromthe region of the gaps within and between the hollow electrodes 24 and36.

Electrodes 22 and 24 include end portions or end walls 44 and 46 whichface one another and define a first gap 48 therebetween. Electrode endwall 44 is suitably slightly cup-shaped or concave where it faceselectrode 46 for the reception of a deposit of low work functionmaterial. Similarly, electrodes 34 and 36 have end portions or end walls50 and 52 which face one another to define a gap 54 therebetween, andelectrode 34 is suitably cup-shaped. The end walls 46 and 52 ofelectrodes 24 and 36 are respectively provided with apertures 55 and 56centrally facing the gap region which provide communication betweenchamber 40 and the region of the gaps, and which are aligned so thatillumination taking place at one gap will also illuminate the oppositegap. No other communication besides apertures 55 and 56 is desirablebetween chambers 32, 40, and 42.

To secure the various electrodes within spacer tubes and 12, theassembly of components as described, with brazing washers in place, israised in temperature to braze the assembly. The interiors of thechambers are evacuated and suitably provided with an internal gaseousenvironment at less than atmospheric pressure. The chambers 32, 40, and42 are hermetically sealed, and communicate only with one anotherthrough apertures 55 and 56.

The spark-gap device according to the present invention is suitablysupported and connected to circuitry to be protected employing a holdergenerally indicated at 66 including spring clips 68 and 70 joined atinsulated base 72 as illustrated in FIG. 1. Spring clips 68 and 70terminate in caps 74 and 76, shown in cross section in FIG. I, employedfor engaging the end flanges of the spark-gap device. The spring clips68 and 70 are adapted to urge the caps against the end flanges to makegood contact therewith, but are not required to form a hermeticallysealed contact.

A spark-gap according to the present invention is connected to a line tobe protected or between a line and ground by means of spring clips 68and 70. A connection for a spark-gap device 78 according to the presentinvention is illustrated in FIG. 2 where end terminals thereof areconnected respectively to voltage supply lines 80 and 82 extending froma source of power to a load 84. When a predetermined voltage level isreached, e.g. as a result of a high voltage transient on the line, gaps48 and 54 break down into an arc discharge, thereby shorting out thehigh voltage transient, and protecting load 84 and other equipment onthe line. The gaps 48 and 54 are suitably spaced such and thepressurization within the spark-gap device is predetermined such that anarc discharge occurs across gaps 48 and 54 at a relatively lowovervoltage value. To use the previous example, spark-gap device 78 maybe set to break down at an overvoltage condition of 350 volts peakacross a line where the operating voltage is 120 volts R.M.S. orapproximately 170 volts peak. Since the gaps 48 and 54 are connected inseries, an arc discharge takes place across both gaps at approximatelythe same time. However, except for the passage provided by apertures 55and 56 and chamber 40, there would be an excessive time lag beforecompletion of an arc discharge. Both gaps would have to fire separatelyand their respective time lags would add. With the present device,substantially simultaneous ionization takes place at both gaps as aresult of the passage formed by apertures 55 and 56, and chamber 40. Notonly does direct gas ionization take place through the passage, but alsothe initiation of an arc discharge across one gap provides radiationilluminating the region of the other gap. This illumination producesphotoelectrons at'an electrode of the opposite gap, which in turn causeionization of the gas in the region of such gap. For example, assuminggap 54 is the first to break down, the arc discharge at gap 54 willilluminate end portion 44 of electrode 22 through apertures 56 and 55.The photons reaching portion 44 will produce photoelectrons which willbe emitted from portion 44 and which, in turn, will cause ionization ofgap 48. As a result, gap 48 breaks down substantially immediately intoan are discharge. The time lag during which the foregoing events takeplace is such that both gaps break down at substantially the same time.The'terms illumination and radiation employed above are meant tocomprehend ultraviolet and/or visible radiation.

A further important advantage of the present invention relates toextinguishing of the arc discharge when an overvoltage condition isremoved. For example, assume the voltage between voltage supply linesand 82 in FIG. 2 drops from an overvoltage of 350 volts peak to a normalI70 volts peak for a volt supply line. At the occurrence of the nextcurrent zero, that is, when the alternating current wave next passesthrough the zero axis, the arc extinguishes at each of the gaps. Thearcs do not then restrike as the line voltage again rises to a normalvolts peak value. By way of explanation, it will be noted that threeseparate gas chambers are provided within the device of the presentinvention, namely, chambers 32, 40, and 42. The three separate gaschambers appear to break up the ionized gas channel, causing fasterdeionization at the end of an overvoltage condition. Moreover, the gasin chamber 40, communicating with'the region of the gaps, is muchcooler, and not ionized to the same degree as the gases in chambers 32and 42. At the occurrence of the first current zero after an overvoltagecondition is removed, the ionized gas appears to be replaced orintermixed with cooler gas through apertures 55 and 56 whereby the gapsdo not restrike. The above explanations are postulated as possiblereasons why the present construction is efiicacious in extinguishing adischarge after an overvoltage condition is passed, and it is understoodthe invention is not limited to any given theory of operation.

The construction according to the present invention may be expanded asillustrated in FIG. 4 wherein a spark-gap device includes fourindividual gap devices, 86, 88, 90, and 92 joined in a seriesconstruction. This configuration is suitable for higher voltageapplications than would be the double gap illustrated in FIGS. 1 and 3.Construction and operation are substantially the same as hereinbeforedescribed in connection with the embodiment of FIGS. 1 and 3. Allelectrodes except the end electrodes are apertured to provideinterconnecting chambers between gaps, as well as a passage for theillumination of the several gaps by a first gap to break down, wherebydischarge will then substantially take place at all gaps. FIG. 5 is across sectional view taken at 55 in FIG. 4, and illustrates aperture 56in electrode 36. The same cross section is equally illustrative of thedevice of FIGS. 1 and 3.

There is provided according to the present invention a small sizespark-gap device which is suitably constructed to break down and providean arc discharge at a relatively low transient voltage value, forexample, at a value just above the normal peak voltage value occurringacross a protected line. In the example given, the breakdown voltage wasapproximately twice the normal peak voltage across the protected line.At the conclusion of a high voltage transient, the spark-gap deviceaccording to the present invention substantially immediatelyextinguishes the arc, that is, the arc is extinguished at the occurrenceof the next current zero of the alternating current wave and does notrestrike.

The device according to the present invention is susceptible tovariation without departing from the inventive concept. For example,although spark-gap device 78 in FIG. 2 is illustrated as being connectedacross a line, without connection of the floating electrodes indicatedat 94, it is understood that such interconnection may in some instancesbe grounded. It is preferred, however, that a construction such asillustrated in FIG. 4 be employed in such instance, wherein centerconnection 96 is grounded with end connections of the devicedisposedacross a voltage supply line.

Moreover, any number of individual gap devices may be arranged in aseries construction of the type illustrated in FIG. 4, with four suchdevices being given only by way of example.

While I have shown and described preferred embodiments of my invention,it will be apparent to those skilled in the art that many other changesand modifications may be made without departing from my invention'in itsbroader aspects. I therefore intend the appended claims to cover allsuch changes and modifications as fall within the true spirit and scopeof my invention.

I claim:

1. A spark-gap device suitable for providing transient protection to aline above a predetermined voltage level, said device comprising:

a first pair of conductive electrodes,

insulating spacer means positioning said first pair of electrodes withopposed portions thereof in facing relation for defining a first gaptherebetween adapted to break down and support an are discharge,

a second pair of conductive electrodes,

insulating spacer means positioning said second pair of electrodes withopposed portions I: therof thereof in facing relation for defining asecond gap therebetween adapted to break down and support an arcdischarge,

one of said second pair of electrodes being electrically connected toone of said first pair of electrodes for providing a series circuitincluding said gaps, said device being constructed so that an arcdischarge across one gap causes illumination of the other gap,

and a first enclosed chamber substantially separate from the region ofsaid gaps and communicating with the region of [at least one of I saidgaps to promote extinguishing of an arc discharge across the said [oneof said] gaps after the cessation of an over-voltage condition acrosssaid gaps in series WhEIC' lH said insulating spacer means cooperatewith said electrodes to enclose the first and second gaps in second andthird separate chambers respectively, said insulating spacer means beingjoined to the respective pairs of electrodes with which they formchambers to hermetically seal said second and third chambers except forcommunication with said first chamber.

I: 2. The device according to claim 1 wherein said in sulating spacermeans cooperate with said electrodes to enclose the first and secondgaps in second and third separate chambers respectively, said firstenclosed chamber communicating with at least one of the other chambers]3. The device according to claim 1 wherein the connected electrodes arehollow and are joined to provide said first enclosed chamber which ishermetically sealed except for communication with said second and thirdchambers,

said connected electrodes being provided with apertures through portionsthereof adjacent said gaps to communicate with said gaps.

4. The device according to claim 3 wherein said electrodes arelongitudinally aligned so that said apertures in said connectedelectrodes provide a line-of-sight path between opposed portions of theremaining electrodes.

5. A spark-gap device suitable for providing transient protection to aline above a predetermined voltage level, said device comprising:

a first hollow enclosure means provided with a first pair of alignedconductive electrodes extending into said first hollow enclosure meansand completing a first chamber therewith, said first pair of electrodeshaving adjacent opposed portions defining a first gap therebetweenwithin said first chamber,

and a second hollow enclosure means provided with a second pair ofaligned conductive electrodes extending into said second enclosure meansand completing a second chamber therewith, said second pair ofelectrodes having adjacent opposed portions defining a second gaptherebetween within said second chamber,

one electrode of said first pair of one electrode of said second pairbeing connected to provide a series electrical circuit including saidgaps,

said connected electrodes being provided with a direct passage betweensaid first and second gaps for providing illumination of at least aportion of one of said gaps by an arc discharge occurring across theother of said gaps, said passage comprising a third chambercommunicating with the region of the gaps in said first and secondchambers said hollow enclosure means being joined to the respectiveelectrodes they enclose to hermetically seal said first and secondchambers except for communication with said third chamber.

[6. The device according to' claim 5 wherein said hollow enclosure meansare joined to the respective electrodes they enclose to providehermetically sealed chambers therewithin except for communication withsaid third chamber.

7. The device according to claim [6 5 wherein said connected electrodesare hollow and are sealed back-to-back to provide a II hermetically sealsaid third chamber [which is hermetically sealed except forcommunication with said first and second chambers, said connectedelectrodes being centrally apertured at said gaps to complete saiddirect passage.

8. The device according to claim 5 wherein said enclosure means comprisespacer means and wherein said spacer means and said electrodes aresubstantially cylindrical, hollow, and aligned, each electrode having an7 end portion adjacent and forming an arc-supporting surface of one ofsaid gaps within-a respective spacer means, a first length of each suchelectrode nextto the end portion having a first diameter, a secondlength of such electrode having a second and larger diameter where suchelectrode is provided with an annular flange joined to an end ofarespective spacer melber] member, and a third length of changingdiameter joining said first and second lengths, said connectedelectrodes being joined at their annular flanges in substantialalignment to form said third chamber therewithin and being centrallyapertured at said gaps to complete said direct passage.

9. The device according to claim 8 wherein said spacer members areformed of ceramic, with said annular flange of each said electrode beingbrazed to an end of a spacer member, and wherein the annular flanges ofsaid connected electrodes are brazed together.

10. The device according to claim wherein said connected electrodes aresubstantially aligned and hollow, extending longitudinally within therespective enclosure means to form said third chamber, and are providedwith apertures where they face the remaining electrodes to complete saidpassage, said apertures providing a line-of-sight path between facingportions of the remaining electrodes and communication with said thirdchamber.

[11. The device according to claim 10 including further enclosure meansand further electrodes extending therewithin in longitudinal alignmentwith said first and second enclosure means, each further electrode beingapertured except for an end electrode, and with the rearward portion ofeach electrode being joined to the next except for an end electrode] 12.The device according to claim 1 wherein said [insulating spacer meanscooperate with said electrodes to enclose said first and second gaps insecond and third chambers respectively, said] connected electrodes[being hollow and protruding] protrude within the respective spacermeans while being joined to provide said first enclosed chamber, saidconnected electrodes being provided with aligned apertures adjacent saidgaps.

13. A spark gap device suitable for providing, transient protection to aline above a predetermined voltage level, said device comprising:

a first hollow enclosure means provided with a first pair of alignedconductive electrodes extending into said first hollow enclosure meansand completing a first chamber therewith, said first pair of electrodeshaving adjacent opposed portions defining a first gap therebetweenwithin said first chamber,

and a second hollow enclosure means provided with a second pair ofaligned conductive electrodes extending in to said second enclosuremeans and completing a second chamber there with, said second pair ofelectrodes having adjacent opposed portions defining a second gaptherebetween within said second chamber,

one electrode of said first pair and one electrode of said second pairbeing unitary to provide a series electrical circuit including saidgaps,

said one electrode of said first pair and said one electrode of saidsecond pair being provided with a direct passage between said first andsecond gaps for providing illumination of at least a portion of one ofsaid gaps by an arc discharge occurring across the other of said gaps,

said hollow enclosure means being joined to the respective electrodesextending therewithin to hermetically seal said first and secondchambers'except for said direct passage.

14. A spark gap device suitable for providing transient protection to aline above a predetermined voltage level, said device comprising:

a first hollow enclosure means provided with a first pair of alignedconductive electrode means completing a first chamber therewith, saidfirst pair of electrode means having adjacent opposed portions defininga first gap therebetween within said first chamber,

and a second hollow enclosure means provided with a second pair ofaligned conductive electrode means completing a second chamber with saidsecond hollow enclosure means, said second pair of electrode meanshaving adjacent opposed portions defining a second gap therebetweenwithin said second chamber,

one electrode means of said first pair being unitary with one electrodemeans of said second pair, the remaining electrode means of said pairsextending into the respective hollow enclosure means,

said unitary electrode means being provided with a direct passagebetween said first and second gaps for providing illumination of atleast a portion of one of said gaps by an arc discharge occurring acrossthe other of said gaps,

said hollow enclosure means being joined to the respective electrodemeans with which they complete a chamber to hermetically seal said firstand second chambers except for said direct passage.

15. A spark gap device suitable for providing transient protection to aline above a predetermined voltage level, said device comprising:

first and second aligned conductive electrode means, and a first hollowenclosure means therebetween completing a first chamber with said firstand second electrode means, said first and second electrode means havingadjacent opposed portions defining a first gap therebetween within saidfirst chamber, said first conductive electrode means extending into saidfirst hollow enclosure means,

a third electrode means aligned with the first and second electrodemeans, and a second hollow enclosure means between the second and thirdelectrode means completing a second chamber with the second and thirdelectrode means, said second and third electrode means having adjacentopposed portions defining a second gap therebetween within said secondchamber, said third conductive electrode means extending into saidsecond hollow enclosure means,

said second electrode means being provided with a direct passage betweensaid first and second gaps for providing illumination of at least aportion of one of said gaps by the arc discharge occurring across theother of said gaps,

said hollow enclosure means being joined to the respective electrodemeans with which they complete a chamber to hermetically seal said firstand second chambers except for said direct passage.

16. The device according to claim 15 wherein said first and thirdelectrode means are disposed in juxtaposed facing spaced relationin thelongitudinal direction of said device, with. the second electrode meansforming a barrier therebetween except for said direct passage, saidfirst and second gaps being formed between lateral exposed faces 9 ofsaid second electrode means and the said first and third electrode meansrespectively.

I 7. The device according to claim wherein said enclosure means comprisespacer means and are substantially cylindrical, hollow, and aligned,said electrode means extending within said enclosure means also beingsubstantially hollow and aligned, each having an end portion adjacentand forming an are supporting surface of one of said gaps within arespective enclosure means, and each being provided with an annularflange joined to an end of the respective enclosure means.

18. A spark-gap device sutiable for providing transient protection to aline above a predetermined voltage level, said device comprising:

a first hollow enclosure means provided with a first pair of alignedconductive electrodes extending into said first hollow enclosure meansand completing a first chamber therewith, said first pair of electrodeshaving adjacent opposed portions defining a first gap therebetweenwithin said first chamber,

a second hollow enclosure means provided with a second pair of alignedconductive electrodes extending into said second enclosure means andcompleting a second chamber therewith, said second pair of electrodeshaving adjacent opposed portions defining a second gap therebetweenwithin said second chamber,

one electrode of said fi rst pair and one electrode of said second pairbeing connected to provide a series electrical circuit including saidgaps,

said connected electrodes being substantially aligned and hollow,extending longitudinally within the respective enclosure means to form athird chamber,

and further enclosure means and further electrodes extending therewithinin longitudinal alignment with said first and second enclosure means forproviding further gaps in further chambers,

each electrode being apertured except for end electrodes, and with therearward portion of each electrode being joined to the next except forend electrodes,

said apertures providing a direct line-of-sight passage between gaps forproviding illumination therebetween when an arc discharge occurs acrossat least one of said gaps,

said hollow enclosure means being joined to the respective electrodesthey enclose to hermetically seal the chambers formed thereby except forcommunication between chambers provided by said apertures.

1. A spark-gap device suitable for providing transient protection to aline above a predetermined voltage level, said device comprising: afirst pair of conductive electrodes, insulating spacer means positioningsaid first pair of electrodes with opposed portions thereof in facingrelation for defining a first gap therebetween adapted to break down andsupport an arc discharge, a second pair of conductive electrodes,insulating spacer means positioning said second pair of electrodes withopposed portions (therof) thereof in facing relation for defining asecond gap therebetween adapted to break down and support an arcdischarge, one of said second pair of electrodes being electricallyconnected to one of said first pair of electrodes for providing a seriescircuit including said gaps, said device being constructed so that anarc discharge across one gap causes illumination of the other gap, and afirst enclosed chamber substantially separate from the region of saidgaps and communicating with the region of (at least one of) said gaps topromote extinguishing of an arc discharge across the said (one of said)gaps after the cessation of an over-voltage condition across said gapsin series (.) , wherein said insulating spacer means cooperate with saidelectrodes to enclose the first and second gaps in second and thirdseparate chambers respectively, said insulating spacer means beingjoined to the respective pairs of electrodes with which they formchambers to hermetically seal said second and third chambers except forcommunication with said first chamber.
 3. The device according to claim1 wherein the connected electrodes are hollow and are joined to providesaid first enclosed chamber which is hermetically sealed except forcommunication with said second and third chambers, said connectedelectrodes being provided with apertures through portions thereofadjacent said gaps to communicate with said gaps.
 4. The deviceaccording to claim 3 wherein said electrodes are longitudinally alignedso that said apertures in said connected electrodes provide aline-of-sight path between opposed portions of the remaining electrodes.5. A spark-gap device suitable for providing transient protection to aline above a predetermined voltage level, said device comprising: afirst hollow enclosure means provided with a first pair of alignedconductive electrodes extending into said first hollow enclosure meansand completing a first chamber therewith, said first Pair of electrodeshaving adjacent opposed portions defining a first gap therebetweenwithin said first chamber, and a second hollow enclosure means providedwith a second pair of aligned conductive electrodes extending into saidsecond enclosure means and completing a second chamber therewith, saidsecond pair of electrodes having adjacent opposed portions defining asecond gap therebetween within said second chamber, one electrode ofsaid first pair of one electrode of said second pair being connected toprovide a series electrical circuit including said gaps, said connectedelectrodes being provided with a direct passage between said first andsecond gaps for providing illumination of at least a portion of one ofsaid gaps by an arc discharge occurring across the other of said gaps,said passage comprising a third chamber communicating with the region ofthe gaps in said first and second chambers(.) , said hollow enclosuremeans being joined to the respective electrodes they enclose tohermetically seal said first and second chambers except forcommunication with said third chamber.
 7. The device according to claim(6) 5 wherein said connected electrodes are hollow and are sealedback-to-back to (provide a) hermetically seal said third chamber (whichis hermetically sealed) except for communication with said first andsecond chambers, said connected electrodes being centrally apertured atsaid gaps to complete said direct passage.
 8. The device according toclaim 5 wherein said enclosure means comprise spacer means and whereinsaid spacer means and said electrodes are substantially cylindrical,hollow, and aligned, each electrode having an end portion adjacent andforming an arc-supporting surface of one of said gaps within arespective spacer means, a first length of each such electrode next tothe end portion having a first diameter, a second length of suchelectrode having a second and larger diameter where such electrode isprovided with an annular flange joined to an end of a respective spacer(melber) member, and a third length of changing diameter joining saidfirst and second lengths, said connected electrodes being joined attheir annular flanges in substantial alignment to form said thirdchamber therewithin and being centrally apertured at said gaps tocomplete said direct passage.
 9. The device according to claim 8 whereinsaid spacer members are formed of ceramic, with said annular flange ofeach said electrode being brazed to an end of a spacer member, andwherein the annular flanges of said connected electrodes are brazedtogether.
 10. The device according to claim 5 wherein said connectedelectrodes are substantially aligned and hollow, extendinglongitudinally within the respective enclosure means to form said thirdchamber, and are provided with apertures where they face the remainingelectrodes to complete said passage, said apertures providing aline-of-sight path between facing portions of the remaining electrodesand communication with said third chamber.
 12. The device according toclaim 1 wherein said (insulating spacer means cooperate with saidelectrodes to enclose said first and second gaps in second and thirdchambers respectively, said) connected electrodes (being hollow andprotruding) protrude within the respective spacer means while beingjoined to provide said first enclosed chamber, said connected electrodesbeing provided with aligned apertures adjacent said gaps.
 13. A sparkgap device suitable for providing transient protection to a line above apredetermined voltage level, said device comprising: a first hollowenclosure means provided with a first pair of aligned conductiveelectrodes extending into said first hollow enclosure means andcompleting a first chamber therewith, said first pair of electrodeshaving adjacent opposed portions defining a first gap therebetweenwithin said first chamber, and a second hollow enclosure means providedwith a second pair of aligned conductive electrodes extending into saidsecond enclosure means and completing a second chamber therewith, saidsecond pair of electrodes having adjacent opposed portions defining asecond gap therebetween within said second chamber, one electrode ofsaid first pair and one electrode of said second pair being unitary toprovide a series electrical circuit including said gaps, said oneelectrode of said first pair and said one electrode of said second pairbeing provided with a direct passage between said first and second gapsfor providing illumination of at least a portion of one of said gaps byan arc discharge occurring across the other of said gaps, said hollowenclosure means being joined to the respective electrodes extendingtherewithin to hermetically seal said first and second chambers exceptfor said direct passage.
 14. A spark gap device suitable for providingtransient protection to a line above a predetermined voltage level, saiddevice comprising: a first hollow enclosure means provided with a firstpair of aligned conductive electrode means completing a first chambertherewith, said first pair of electrode means having adjacent opposedportions defining a first gap therebetween within said first chamber,and a second hollow enclosure means provided with a second pair ofaligned conductive electrode means completing a second chamber with saidsecond hollow enclosure means, said second pair of electrode meanshaving adjacent opposed portions defining a second gap therebetweenwithin said second chamber, one electrode means of said first pair beingunitary with one electrode means of said second pair, the remainingelectrode means of said pairs extending into the respective hollowenclosure means, said unitary electrode means being provided with adirect passage between said first and second gaps for providingillumination of at least a portion of one of said gaps by an arcdischarge occurring across the other of said gaps, said hollow enclosuremeans being joined to the respective electrode means with which theycomplete a chamber to hermetically seal said first and second chambersexcept for said direct passage.
 15. A spark gap device suitable forproviding transient protection to a line above a predetermined voltagelevel, said device comprising: first and second aligned conductiveelectrode means, and a first hollow enclosure means therebetweencompleting a first chamber with said first and second electrode means,said first and second electrode means having adjacent opposed portionsdefining a first gap therebetween within said first chamber, said firstconductive electrode means extending into said first hollow enclosuremeans, a third electrode means aligned with the first and secondelectrode means, and a second hollow enclosure means between the secondand third electrode means completing a second chamber with the secondand third electrode means, said second and third electrode means havingadjacent opposed portions defining a second gap therebetween within saidsecond chamber, said third conductive electrode means extending intosaid seconD hollow enclosure means, said second electrode means beingprovided with a direct passage between said first and second gaps forproviding illumination of at least a portion of one of said gaps by thearc discharge occurring across the other of said gaps, said hollowenclosure means being joined to the respective electrode means withwhich they complete a chamber to hermetically seal said first and secondchambers except for said direct passage.
 16. The device according toclaim 15 wherein said first and third electrode means are disposed injuxtaposed facing spaced relation in the longitudinal direction of saiddevice, with the second electrode means forming a barrier therebetweenexcept for said direct passage, said first and second gaps being formedbetween lateral exposed faces of said second electrode means and thesaid first and third electrode means respectively.
 17. The deviceaccording to claim 15 wherein said enclosure means comprise spacer meansand are substantially cylindrical, hollow, and aligned, said electrodemeans extending within said enclosure means also being substantiallyhollow and aligned, each having an end portion adjacent and forming anarc supporting surface of one of said gaps within a respective enclosuremeans, and each being provided with an annular flange joined to an endof the respective enclosure means.
 18. A spark-gap device sutiable forproviding transient protection to a line above a predetermined voltagelevel, said device comprising: a first hollow enclosure means providedwith a first pair of aligned conductive electrodes extending into saidfirst hollow enclosure means and completing a first chamber therewith,said first pair of electrodes having adjacent opposed portions defininga first gap therebetween within said first chamber, a second hollowenclosure means provided with a second pair of aligned conductiveelectrodes extending into said second enclosure means and completing asecond chamber therewith, said second pair of electrodes having adjacentopposed portions defining a second gap therebetween within said secondchamber, one electrode of said first pair and one electrode of saidsecond pair being connected to provide a series electrical circuitincluding said gaps, said connected electrodes being substantiallyaligned and hollow, extending longitudinally within the respectiveenclosure means to form a third chamber, and further enclosure means andfurther electrodes extending therewithin in longitudinal alignment withsaid first and second enclosure means for providing further gaps infurther chambers, each electrode being apertured except for endelectrodes, and with the rearward portion of each electrode being joinedto the next except for end electrodes, said apertures providing a directline-of-sight passage between gaps for providing illuminationtherebetween when an arc discharge occurs across at least one of saidgaps, said hollow enclosure means being joined to the respectiveelectrodes they enclose to hermetically seal the chambers formed therebyexcept for communication between chambers provided by said apertures.